1. Field of the Invention.
This invention relates to new and improved, non-invasive method and apparatus for instantaneous flow measurement of a segmented fluid stream in an optically transparent conduit of a continuous flow system.
2. Description of the Prior Art
Although instantaneous flow measurement methods and apparatus are known in the prior art for detecting flow in fluid conduits, the same will, in many instances, be found to be invasive in requiring the disposition of detecting means within the conduit, and to thus be generally inapplicable for use in continuous flow, automated analysis systems which operate through use of precisely fluid-segmented liquid stream. More specifically, and taking for example those prior art flow measurement methods and apparatus which operate through use of a heat-sensitive detecting device in the nature of a thermistor which is disposed in the conduit within the fluid stream, it will be readily understood by those skilled in this art that the presence of the detecting device in the fluid stream presents an obstruction to fluid flow in the conduit, which obstruction can operate to generate turbulence with attendant destruction of the essentially precise segmentation of the fluid stream. As a result, such prior art methods and apparatus would not be applicable for use in automated analysis systems which operate through use of precisely segmented fluid streams. Additional problems which would arise regarding the use of invasive, heat sensitive flow detecting means in continuous flow, automated analysis systems which operate through use of precise fluid-segmented liquid streams, include the necessity for precise calibration thereof in accordance with each of the different heat capacities of each of the different liquids which may be flowing in each of the different conduits of a multi-conduit or multi-channel analysis system; as well as the insulating effects of the fluid segments on the heat sensitive flow detecting device which can lead to erroneous readings. Also, it is believed clear that the disposition of flow detecting means in any conduit through which a fluid is being pumped in any kind of system can only function to increase the flow resistance through said conduit to thus materially increase the energy required for fluid pumping, and especially in those instances wherein the conduit is of small I.D.; while the disposition of the flow detecting means in the conduit can lead to corrosion of the former in those instances wherein the fluid flowing in the conduit is corrosive. Too, the actual disposition of the flow detecting means in the conduit can present manufacturing problems, especially in those instances wherein the conduit I.D. is small, which problems would, of course, be magnified in those instances wherein it becomes necessary or desirable to change the location in the conduit at which instantaneous flow measurement is to be made to thus require re-location of the detecting means in the conduit.
Although non-invasive, prior art instantaneous flow measurement method and apparatus in the nature, for example, of the video analysis system disclosed in the article, "Video Analysis of Low Flow Rates" by A.D. Falco, W.R. Tompkins and M. Intaglietta s published in Microvascular Research 6, pp. 362-365 (1973) are known, the same may be understood to be of particularly complex and expensive design and construction in requiring a CRT or like device, and complex logic including special switching circuitry to generate and control the position of a single "window" which isolates the area of interest in a television video frame; and to additionallycall for the introduction of a suitable dye into the fluid stream to insure sufficient video contrast.